DE3413698A1 - SEALING DEVICE, IN PARTICULAR FOR USE IN A PNEUMATIC SPRING - Google Patents

Description

Patent attorneys Dipl.-Ing. H. Weicx * £ äkn, Diil.-Phys. Dr. K. Fincke

Dipl.-Ing. F. A. Weickmann, Dipl.-Chem. B. Huber Dr.-Ing. H. Liska, Dipl.-Phys. Dr. J. Prechtel

Gas Spring Company 34

8000 MÜNCHEN 86 Division Of POSTFACH 860820

Fichtel & Sachs Industries möhlstrasse22

TELEPHONE (0 89) 980352! TELEX 522621

92 County Line Road Telegram patentweickmannmonchen

Colmar, Pennsylvania 18915

V.St.A. ^{¥ A}

Sealing device, in particular for use in a

pneumatic spring

The invention relates to a sealing device of the type described in the preamble of claim 1.

Such sealing devices arranged between a movable piston rod and a stationary housing body are intended to prevent the pressurized fluid from escaping along the piston rod.

Pneumatic springs are known in the cylinder cavity of which there is a fluid under high pressure, for example air or nitrogen. An attempt was made to allow the gas to escape from the cylinder along the piston rod a chamber containing a liquid, e.g. oil, which is located in the vicinity of the open end wall through which the piston performs its alternating movement.

Such pneumatic springs can be used in resilient columns for vibration-free documents, as they are in U.S. Patent 3,856,287. U.S. Patent 4,263,488 and the prior art cited therein show as a further application, an arrangement for fixing the rear door of a station wagon in the open position. aside from that For example, springs of the type in question can be used in pneumatic suspensions, as for example in U.S. Patent 4,030,716.

Feathers with a fluid chamber near the open one End walls have excellent sealing properties for the compressed gas. But even works for them the gas due to the pressure difference on the two sides of the between the gas chamber and the liquid chamber lying fixed seal may pass this. That then collects in the liquid chamber Gas works its way through the seal arranged on the open end wall much faster than the liquid. The increased gas concentration in the liquid chamber affects the lubrication in the bulkhead seal through the liquid and also leads to a certain position dependency of the gas spring at certain Mounting types. In addition, the load on the seal between the gas chamber and the liquid chamber causes which is proportional to the pressure difference, friction and wear of the seal

The invention is based on the object of developing a sealing device of the generic type in such a way that the disadvantages appearing in the preceding description are avoided.

This object is achieved by a sealing device with the features of claim 1.

Advantageous refinements and developments of the invention are the subject matter of the subclaims, to which herewith reference is made to shorten the description. The use of a sealing device is also included in these subclaims described according to the invention in a pneumatic spring.

In the case of the sealing device according to the invention, this is in the vicinity of the open end wall and the liquid chamber provided seal firmly, while the seal between the gas chamber and the liquid chamber is floating is so they can move freely towards the fixed seal

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and slide away from her. As soon as the tight seal leaks or wears out, the gas chamber and liquid chamber moves in a floating manner separating them from each other Seal towards the solid seal when the liquid, usually oil, slowly moves through the solid Seal works through it.

During this slow movement of the floating seal arises on it as a result of the minimal pressure difference little friction and wear between their two sides. The low pressure difference on the floating arranged seal also leads to the fact that only slight gas penetration takes place through them into the liquid chamber. This ensures that liquid will be in contact with the solid seal throughout its life stands.

If there are minimal amounts of gas in the liquid chamber, this applies to all temperatures occurring during operation and directional orientations of the gas spring ensure sufficient lubrication for the tight seal. Also leakage losses the tight seal is small because liquid, especially oil, moves at a slower rate through this seal works as a gas.

The floating seal is optionally fixed in the vicinity of the fixed seal by a stop and then acts as a secondary or safety seal, by means of which the remaining gas and liquid pressure in the pneumatic spring is maintained.

In another embodiment, floating between the arranged seal and the fixed seal a mechanical compression spring can be provided. This is used for pre-tensioning the floating seal in its (innermost) starting position within the gas spring and acts resiliently opposed to movement of the floating seal towards the fixed seal when through the fixed seal

Seal fluid loss takes place. This mechanical counteracts the movement of the floating seal. Resistance increases the pressure differential between the two sides of the floating seal and thereby causes a more uniform distribution of the pressure difference between the gas chamber and the atmosphere both the floating and the fixed seal.

The seal construction according to the invention has a longer life, longer shelf life and a greater one Operating temperature range and causes that with it equipped pneumatic spring with regard to its position orientation in the installed state less sensitive is.

It is also possible to use different types of seal / gas / oil combinations to use that would otherwise not be feasible due to incompatibilities of the materials used are. This results from the fact that the gas behind the piston opposite the liquid in the between solid and floating seal lying chamber is isolated.

The invention is explained in more detail below with reference to the drawings:

Fig. 1 shows a sectional view of a seal according to the invention in a pneumatic spring,

Fig. 2 shows a sectional view of a seal according to a further embodiment of the invention,

Fig. 3 shows a sectional view of a seal according to a third embodiment of the invention.

The sealing device shown in Fig. 1 is located in a pneumatic spring 10, which is an axially elongated Has cylinder 11 with a circular cross-section. The associated piston assembly includes a cylindrical one Piston rod 12 and a piston body 13, which is attached to

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the smaller-diameter end of the piston rod 12 in the cylinder space is axially fixed. The outer circular surface of a Koltienring 14 is with the inner cylinder wall in sliding contact. The piston ring 14 is axially with slight play between the piston body 13 and one with openings provided metal disc 15 taken. The latter has a sharp-angled rectangular cross-section and rests on one Piston rod shoulder 12.

The radial play between the piston body 13 and the cylinder wall is shown exaggerated for better visibility. The diameter of the piston body 13 is sufficiently larger than that of the disk 15 to allow radial guidance for the inner end of the piston rod 12.

The chamber 17 located behind the piston body 13 contains a gas, preferably air or nitrogen, which is at a pressure substantially higher than atmospheric pressure. if the piston rod 12 moves outward from the cylinder 11 under the spring force of this compressed gas Gas from the chamber 17 only through a throttle opening (not shown) in the piston body 13 flow. When the piston rod moves in the opposite direction, the piston ring 14 opens an additional flow path through the openings of the disk 15 and the gap between the piston body 13 and the cylinder corresponding to the play 11, as described in more detail in US Pat. No. 4,263,488 and the prior art cited therein.

The piston rod 12 is also in its axial movement through an opening 19 in the end wall 20 of the cylinder 11 axially guided by a guide bush 21 arranged in the vicinity of this end wall. A solid annular The seal 22 is made by means of a spacer ring 23 and an inner rib formed in the side wall of the cylinder 11 24 held against the socket 21. The seal 22 is made of elastomeric material and has an outer annular shape

'V 34 1 3603

Lip 26, which rests against the cylinder wall, and an inner annular lip 27, which is connected to the piston rod 12 in sliding engagement. The seal 22 is reinforced and seals by a flat, embedded metal ring 28 the compressed fluids in the cylinder cavity.

The opposite end of the cylinder 11 is closed by an end wall 30 on which a fastening eye 31 is mounted. A fastening eye 33 is also mounted on the outer end of the piston rod 12. If the pneumatic Spring 10 is used to hold the tailgate of a station wagon under pretension in its open position, the fastening eye 31 is rotatably mounted on the body and the fastening eye 33 is rotatably mounted on the tailgate.

at a distance from the above-mentioned inner rib 24 is on the side wall of the cylinder 11 another inward protruding rib 35 is formed. When the piston rod 12 is pushed out of the cylinder cavity by the compressed gas is, the extension of the piston rod is limited by the fact that the disc 15 comes to rest on the rib 35.

Between the inner ribs 24 and 35, a floating annular seal 37 is freely slidably disposed on the Piston rod 12 and the cylinder wall rests in a sealing manner. The seal 37 is made of elastomeric material and has an outer annular lip 38 that slides on the cylinder wall, and an inner annular lip 39 that slides on the Piston rod 12 rests in a sliding manner. The seal 37 is reinforced by a metal ring 40 that sits on top of the inner rib 24 facing side is attached to it. The ring 40 is dimensioned so that it abuts against the inner rib 24 comes. It is also made strong enough to withstand the gas pressure prevailing in chamber 17, without deforming or stepping over the rib.

In the manufacture of the pneumatic spring 10, the cylinder cavity is first of all using a known method with a

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high pressure gas, preferably air or nitrogen, filled. Then a liquid, preferably Oil of moderate viscosity, introduced by known methods, the chamber 42 between the seals 22 and 37 fills. A sufficiently large amount of liquid is pumped into this chamber to seal the seal 37 against the inner one To let slide rib 35, with all the gas from this chamber in the chamber 17 is brought.

As will be explained in more detail below in connection with FIG. 3, to support the displacing effect of the Fluid on the seal 37 a mechanical compression spring can be provided, which the seal 37 against the Rib 35 presses.

The oil in chamber 42 slowly works its way through seal 22 as it leaks or wears out. While this time the floating seal 37 moves in the direction of the fixed seal 22. During this movement the floating seal 37, however, the pressure difference between its two sides is only minimal, so that they experiences little friction or wear and accordingly only minimal gas permeation through them into the chamber takes place. Therefore, the seal 22 is in contact with oil throughout its life, so that they all Operating temperatures and positions of the pneumatic spring 10 is excellently lubricated.

The floating seal 37 may strike, as indicated by dash-dotted lines 37A the inner rib 24 and then acts as a secondary or safety seal, removing the remaining gas and Maintains oil pressure in the pneumatic Fedep.

The modified seal shown in Fig. 2 is with the exception of the differences shown and described below identical to the seal according to FIG. 1. The inner rib 35 of Fig. 1 is in close proximity by two

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H 3413638

arranged inner ribs 44 and 45 replaced, between which an additional guide bushing 47 is anchored.

The guide bushing 47 forms an additional bearing for the piston rod 12. In addition, the bushing 47 has one of the Chamber 17 facing annular shoulder 48 on which the disc 15 of the piston assembly can strike. This will the disc is kept away from the respective inner rib when the piston rod 12 is in its extended position is located, so that the separation friction is reduced.

The bushing 47 also has an annular shoulder 49 facing the chamber 42 on which the floating shoulder Seal 37 can strike. This creates a tilt-free stop point for the latter during filling of gas and oil.

It has been shown that the effectiveness of the floating Seal 37 can be increased by the fact that a mechanical spring is also provided, which it biases against the rib 35, i.e. in its innermost position in which it is fully seated. A corresponding embodiment the invention is shown in FIG. With the exception of the deviations resulting from the following description the embodiment with those of FIGS. 1 and 2 is identical.

The inner rib 24 is moved as shown in FIG. 3 in the cylinder 11 further inward, so that space for a bushing 50 to Guiding of a spring is created, which is gripped between the fixed seal 22 and the rib 24. The socket 50 is in internally offset and can thus accommodate a mechanical compression spring 54, which is between a shoulder 56 of the socket 50 and the floating seal 37 acts. If desired, one or more additional guide bushings 58 can be provided which ensure that the spring 24 does not touch the inner surface of the cylinder 11 and damage it. A Spacer ring 60 which, if desired, can take the form of bushing 47 in

Fig. 2 may have serves as a stop for the floating Seal 37 and prevents it from being damaged by contact with the rib 35.

The mechanical spring 54 has two functions. It ensures that the floating seal 37 has the desired innermost in Fig. 3 (and in Fig. 2 in solid lines) shown fully seated position when the pneumatic Feather is filled during manufacture. Second, it increases the pressure difference between the two sides of the floating seal 37, i.e. between the gas chamber 17 and the liquid chamber 42, by preventing the movement of the floating seal 37 towards the fixed seal 22 due to leaks (due to wear and timing) opposes resilient resistance. The said pressure difference between the two sides of the Seal 37 gradually increases in size when the mechanical spring 54 with progressive fluid loss through the solid Seal 22 is compressed. This action of the spring 54 distributes the pressure difference between those under high pressure standing gas chamber and the atmospheric pressure more uniformly on the floating seal 37 and the fixed Seal 22 and thereby improves the sealing effect of the combination of floating and fixed seal.

The invention is of course not restricted to the embodiments presented above. So can For example, the floating seal consist of a metal ring on which one sliding on the piston rod inner O-ring seal and an outer O-ring seal sliding on the cylinder wall are mounted.

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Claims (8)

Patent attorneys Dipl.-Ing. H. ¥ eickmahn, Oi »l. Phys. Dr. K. Fincke Dipl.-Ing. R A.Weickmann, Dipl.-Chem. B. Huber Dr.-Ing. H. LiSKA, Oipl.-Phys. "Dr. J. Prechtel 8000 MUNICH 86 ^ Λ 1 POST BOX 860 820 0 ^ 1 MÖHLSTRASSE 22 TELEFON (089) 980352 TELEX 5 22 621 TELEGRAM PATI.NTWEICKMANN MÖNCHEN patent claims 1. Sealing device for use between a piston rod and a side wall and two end walls having housing in which a piston carried by the piston rod can be moved back and forth and in which there is a Pressurized fluid is located with elastomeric sealant attached to the piston rod are in sliding engagement and are ^ in the vicinity of that end wall of the housing through which the piston can be acted upon by the reciprocating movement, characterized in that that between the elastomeric sealing means (22) and the piston (13) a floating sealing member (37) is provided which with the piston rod (12) and the side wall of the housing (11) in sliding engagement stands, and that stop means (35) are provided on which the floating sealing member (37) comes to rest and that between the elastomeric sealing means (22) and the piston (13) from the side wall of the housing (11) protrude inward and are arranged at a distance from the elastomeric sealing means (22), so that the floating arranged sealing member (37) is movable between the elastomeric sealing means (22) and the stop means. 2. Sealing device according to claim 1, characterized in that the floating arranged sealing member (37) and the elastomeric sealing means (22) between them limit a chamber (42) of variable size, in which there is a liquid. 3. Sealing device according to claim 1, characterized in that the floating sealing member (37) is connected to the piston rod (12) and the side wall of the housing (11) slidingly engaged elastomeric sealing member (38) and a rigid reinforcing member (40) interposed between the elastomeric sealing member (38) and the elastomeric Sealing means (22) is arranged. 4. Sealing device according to claim 3, characterized in that the elastomeric sealing member (38) and the reinforcing element (40) are firmly connected with each other. 5. Sealing device according to claim 1, characterized in that second stop means (24) are provided on which the floating arranged sealing member (37) comes to rest and in the vicinity of the elastomeric sealing means (22) of the side wall of the housing (11) extends inward. 6. Sealing device according to claim 1, characterized in that a bushing (47) mounted on the side wall of the housing (11) is provided which forms a stop for the floating sealing member (37) and the piston (13). 7. Sealing device according to claim 1, characterized in that between the floating sealing member (37) and the elastomeric Sealing means (22) resilient means (54) are arranged, which resiliently the floating sealing member (37) pretension in the direction of the first-mentioned attachment means and a movement of the floating sealing processing member of these stop means away resilient resistance oppose. 8. Pneumatic spring characterized by the use of the sealing device according to one or more of the preceding Expectations, said housing being formed by a cylinder which a side wall, a closed end wall (30) and has an end wall (20) provided with an opening (19) through the opening of which the piston rod (12) is inserted into a sealed cavity formed in the cylinder (11) and filled with a pressurized fluid in and out can be moved out of it, wherein further the piston (13) is axially movable in the cavity and finally the floating sealing member (37) enclosing the piston rod (12) in a sealing manner.